1. Field of the Invention
The present invention relates generally to fluid mixing and delivery devices. More particularly, the invention concerns an improved apparatus for mixing beneficial agents with parenteral liquids and for infusing the mixture into a patient at specific rates over extended periods of time.
2. Discussion of the Invention
Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes of the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacudic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus.
Devices from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder are well known in the prior art. Such bladder, or "balloon" type devices are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry. The devices of the aforementioned patents also disclose the use of fluid flow restrictors external of the bladder for regulating the rate of fluid flow from the bladder.
The prior art bladder type infusion devices are not without drawbacks. Generally, because of the very nature of the bladder or "balloon" configuration, the devices are unwieldly and are difficult and expensive to manufacture and use. Further, the devices are somewhat unreliable and their fluid discharge rates are frequently imprecise.
A much more sophisticated fluid delivery apparatus is described in U.S. Pat. No. 5,019,047 issued to the present inventor. This device eliminates the bladder altogether and makes use of recently developed elastomeric films and similar materials, which, in cooperation with a plate-like base define a fluid chamber that contains the fluid which is to be dispensed. The elastomeric film membrane controllably forces fluid within the chamber into fluid flow channels provided in the base. In one form of the apparatus of the invention, a thin, planar shaped flow rate control member is strategically located within the chamber to precisely control the rate of flow of the liquid toward the fluid flow channels. The flow rate control member can be very thin and can be selected to have a very precise degree of permeability so that the rate of flow of fluid into the fluid flow channels can be controlled with great accuracy.
The apparatus of the present invention comprises an improvement upon the device described in the U.S. Pat. No. 5,019,047 by providing a novel means for charging the device with a mixing subsystem that includes cooperating vial assemblies, one of which contains a parenteral fluid and the other of which contains a substrate upon which an additive such as a beneficial agent is immobilized or removably affixed.
Like the earlier device, the device of the present invention uses the state-of-the-art thin membranes and films to permit the construction of compact, low profile, laminated structures which are easy to use and inexpensive to manufacture. When the devices of the invention are to be used with ambulatory patients they are constructed of flexible materials and are provided with a thin adhesive backing which permits the device to be conveniently self-affixed to the patient's arm or other parts of the body.
The device of the invention can be used for mixing virtually any type of beneficial agent such as a drug or other pharmaceutical, with a parenteral fluid such as a diluent. The drug and diluent can be separately packaged and stored until time of use. Following mixing, the device can be used to controllably infuse the mixture which may comprise antibiotics, hormones, steroids, blood anti-clotting agents, analgesics, and like medicinal agents. Similarly, the device can be used for I-V chemotherapy and can accurately deliver fluids to the patient in precisely the correct quantities and at extended microfusion rates over time.